Cast bullet size vs. throat size???

[toad67]

As most of you know, I'm working on a cast bullet load for my 625 in 45 Colt. The 625 has a throat where .452" bullets will hang up when dropped in, but come out easily if pushed. I also have a 25-5 that has an over-sized cylinder where 5 out of 6 .454" bullets fit the same, but one cylinder seems to be even a bit larger.
Would trying the .454" bullets in the 625 with .452" cylinders make sense?

 

[rockquarry]

It's worth trying and will hurt nothing, but also try the .452" bullets. Work up a good accurate load with the .452" bullets and verify by firing several benchrested groups at 25 yards. Then try the same load with the .454" cast bullets. The .452" bullet may shoot better than the .454" as the .454" will be sized to .452" as it travels through the chamber throat, but...there aren't any firm rules when it comes to cast bullets. That's why it pays to experiment with your gun.

 

[StrawHat]

Are you trying to build the most accurate load for each revolver, or one load for both? It makes a big difference. I have a bunch of ACP revolvers, no way would I try for a specific load for each one. Instead, I have found two different loads that the all like. Yes, some like it better than others but they are all good shooters with those loads.

Are you casting your own or buying them? If buying, try the .454. If that shows promise, you can powder coat them if you want to try something larger.

If you cast, you can buy a mold to cast a specific diameter with your alloy.

Kevin

 

[243winxb]

Match barrels groove diameter , plus .0005" to .001" You may find the basic .452" diameter works very well.

This was the early Lyman method when I started casting 50+ years ago.

 

[Mike-AK]

Size your bullets to a hair over bore diameter and if they still hang up in the cylinder throats you can ream the throats out to 0.4525. A bullet sized appropriately to the bore is critical. If your cylinder throats are swaging them down to below bore diameter it can negatively impact accuracy and contribute to leading.

 

[IrishFritz]

The common recommendation is to size your bullets a thousands over cylinder throat diameter. This recommendation was settled on in response to a very large number of first generation Single Action Army Colts that were produced with .454-456 throats and .451 barrels. You don't mention what the bore diameters are of the barrels in each gun and there is the possibility of a thread crush constriction in the barrel lede of the one gun you dropped the slug in. I would think it would be helpful if you were to slug and measure each barrel to see what the true diameters are and that may give you a better understanding of what the correct bullet diameter might be for each. The concern is that firing a bullet undersized for the cylinder throat can result in significant misalignment as the bullet enters the forcing cone of the barrel causing deformation and loss of accuracy. Then too, gas blow bye around the base of the bullet can lead to excessive leading in the cylinder throat which will also degrade accuracy. It seems easier to work around oversize cylinders than undersized and the point made above about reaming the cylinder throats is well said. Good luck with all. IrishFritz

 

[mikld]

I normally measure all the cylinder throats on my revolvers and size bullets to the same diameter. (I prefer measurements, not "drop through", "push through" etc.) I also slug the barrels to make sure groove diameter is smaller than throat diameter. In my experience with 3, 44 Magnum revolvers and 2, 357 Magnum revolvers, bullets larger than throat diameter (.002"+) will spray lead on the cylinder face and frame, and smaller than throat diameter often leads throat and often the barrel.

 

[StrawHat]

The Model 25-5 has 5 groove rifling. The Model 625 may have 5 or 6 groove rifling. I would size .001 over your largest throat. Then push that down he bore. Look at the imprint of the rifling. That will tell you if you are big enough. If not, then worry about enlarging the throats.

Too many folks worry that throats are too large or too small before they even fire the piece.

Kevin

 

[toad67]

Are you trying to build the most accurate load for each revolver, or one load for both? It makes a big difference. I have a bunch of ACP revolvers, no way would I try for a specific load for each one. Instead, I have found two different loads that the all like. Yes, some like it better than others but they are all good shooters with those loads.

Are you casting your own or buying them? If buying, try the .454. If that shows promise, you can powder coat them if you want to try something larger.

If you cast, you can buy a mold to cast a specific diameter with your alloy.

Kevin

To make things simple, on load for both guns would be great, but as you mentioned, I might have to pick one in the middle as you did, and settle on that one.
I've been trying to locate some lead balls locally so I can get a number on my bore size to help out with bullet diameter selection. Also thinking about getting a set of pin gauges just because.
For now though, I'm going to load up some of the .454" bullets with different powders and charges, then go see how they perform.

 

[StrawHat]

To make things simple, on load for both guns would be great, but as you mentioned, I might have to pick one in the middle as you did, and settle on that one.
I've been trying to locate some lead balls locally so I can get a number on my bore size to help out with bullet diameter selection. Also thinking about getting a set of pin gauges just because.
For now though, I'm going to load up some of the .454" bullets with different powders and charges, then go see how they perform.

Pin gauges are the way to go if you want accurate measurements without a lot of hassle. You don’t need a set, just a range, say .451-.458 or whatever you choose.

I still use cast bullets of known diameter. Drop them in, if they pass through, go bigger. I am not scientific about it.

Kevin

 

[rockquarry]

Pin gauges are the way to go if you want accurate measurements without a lot of hassle. You don’t need a set, just a range, say .451-.458 or whatever you choose.

I still use cast bullets of known diameter. Drop them in, if they pass through, go bigger. I am not scientific about it.

Kevin

I've found if they almost but not quite go through, that's okay, too. For the bullet casters, having a variety of cast bullet size dies on hand is also a good idea.

 

[sniper]

Throat/barrel/bullet size

I don't cast any more, and I've had orders of cast bullets, ordered at .358, to be sized somewhat smaller. Not an unusual situation, I hear. Never oversize. My revolver cylinders will pass a .358 ZZ minus pin gauge with the same small amount of force. Soooo, what's a guy to do? Order .359, and size them down to .358, or some other diameter, or just shoot whatever I receive and don't worry?

 

[noylj]

Of course it makes sense.
For revolvers,
1) bullet diameter must be 0.001” over measured barrel groove diameter
and
2) bullet diameter then must be equal to or slightly larger then cylinder’s throats.
If throats are smaller then actual barrel groove diameter, shoot real jacketed bullets.

 

[4barrel]

You could alox the .452 bullet and let dry and measure. Maybe alox it again. It's messy but helps. Powder coat makes them larger also. My SRH has .432 throats and I reworked a .429 LEE mold to make larger and it worked. Lots of ways to improve groups going cheap. 45 L.C. bullets work good with Unique powder.

 

[StrawHat]

…
If throats are smaller then actual barrel groove diameter, shoot real jacketed bullets...

No, if the throats are smaller than the groove diameter, enlarge the throats to the correct size. Not hard to do yourself or ship the cylinder off for the work.

Kevin

 

[toad67]

Hmmm, my .456" pin gauges fall right thru. Looks like I need to go buy some factory jacketed ammo and see how it shoots.

 

[StrawHat]

Jacketed ammunition will still be grabbed by the rifling and shoot okay.

Passing a .456 pin is large, even for a Model 25-5. The only option to correct that cylinder is to get one for a smaller cartridge and have it reamed correctly. If you want to go that route, a WTB on this forum might get you what you need or check eBay.

Kevin

 

[4barrel]

Hmmm, my .456" pin gauges fall right thru. Looks like I need to go buy some factory jacketed ammo and see how it shoots.

Measured on the barrel side? Some of the older molds dropped ..454.

 

[Luke Duke]

The Model 25-5 has 5 groove rifling. The Model 625 may have 5 or 6 groove rifling. I would size .001 over your largest throat. Then push that down he bore. Look at the imprint of the rifling. That will tell you if you are big enough. If not, then worry about enlarging the throats.

Too many folks worry that throats are too large or too small before they even fire the piece.

Kevin

I bought a new 629-6 this year that seems to have tight throats. Seems pretty common from what I've been seeing on this Forum. But my gun shoots great.I've been sizing my cast to .429 and haven't had any leading issue's in barrel and no signs of lead spatter anywhere.

 

[StrawHat]

I bought a new 629-6 this year that seems to have tight throats. Seems pretty common from what I've been seeing on this Forum. But my gun shoots great.I've been sizing my cast to .429 and haven't had any leading issue's in barrel and no signs of lead spatter anywhere.

I agree that S&W has seemly tighten the specs on the chamber throats, across the board. I am more focused on the 45 ACP but aware others are also coming truer to spec.

Hand loading jacketed bullets is fairly basic. Cast bullets are PhD level handloading. Diameters, alloys, seating depth, etc., etc., really can test a reloaders patience. I have simplified my reloading by staying narrowing parameters. I use only simple binary alloys, only two or three powders, and only a couple of bullets. Do I get the ultimate accuracy from each revolver? No, but the accuracy is certainly good enough to harvest game. Besides, my serious competition days are over, but if they were not, I would select the two revolvers I would use in competition and find one load that works in both.

Kevin